Use time mode owner enums in dbus interface

Dbus interface defines time mode owners in xyz::openbmc_project::Time.
Use the enums from the interface instead of repo defined enums and use
the generated code to do convertions between strings and enums.

Update unit tests accordingly.

Change-Id: Ic304aa3b4137375d208bb1702e0f64df512fc5a0
Signed-off-by: Lei YU <mine260309@gmail.com>
diff --git a/bmc_epoch.cpp b/bmc_epoch.cpp
index 7bc6c22..4c8bf60 100644
--- a/bmc_epoch.cpp
+++ b/bmc_epoch.cpp
@@ -110,7 +110,7 @@
         // TODO: throw NotAllowed exception
         return 0;
     }
-    if (timeOwner == Owner::HOST)
+    if (timeOwner == Owner::Host)
     {
         log<level::ERR>("Setting BmcTime with HOST owner is not allowed");
         // TODO: throw NotAllowed exception